A second-generation series of biscyclometalated 2-(5-aryl-thienyl)-benzimidazole and -benzothiazole Ir(III) dppz complexes [Ir(C^N)2(dppz)]+, Ir1-Ir4, were rationally designed and synthesized, where the aryl group attached to the thienyl ring was p-CF3C6H4 or p-Me2NC6H4. These new Ir(III) complexes were assessed as photosensitizers to explore the structure-activity correlations for their potential use in biocompatible anticancer photodynamic therapy. When irradiated with blue light, the complexes exhibited high selective potency across several cancer cell lines predisposed to photodynamic therapy; the benzothiazole derivatives (Ir1 and Ir2) were the best performers, Ir2 being also activatable with green or red light. Notably, when irradiated, the complexes induced leakage of lysosomal content into the cytoplasm of HeLa cancer cells and induced oncosis-like cell death. The capability of the new Ir complexes to photoinduce cell death in 3D HeLa spheroids has also been demonstrated. The investigated Ir complexes can also catalytically photo-oxidate NADH and photogenerate 1O2 and/or •OH in cell-free media.
- MeSH
- Benzothiazoles MeSH
- Photosensitizing Agents pharmacology therapeutic use MeSH
- Dermatitis, Phototoxic * drug therapy MeSH
- Iridium pharmacology MeSH
- Coordination Complexes * pharmacology MeSH
- Humans MeSH
- Lysosomes MeSH
- Cell Line, Tumor MeSH
- Neoplasms * drug therapy MeSH
- Antineoplastic Agents * pharmacology MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
In this work, the mechanism underlying the anticancer activity of a photoactivatable Ir(III) compound of the type [Ir(C^N)2(dppz)][PF6] where C^N = 1-methyl-2-(2'-thienyl)benzimidazole (complex 1) was investigated. Complex 1 photoactivated by visible light shows potent activity against highly aggressive and poorly treatable Rhabdomyosarcoma (RD) cells, the most frequent soft tissue sarcomas of children. This remarkable activity of 1 was observed not only in RD cells cultured in 2D monolayers but, more importantly, also in 3D spheroids, which resemble in many aspects solid tumors and serve as a promising model to mimic the in vivo situation. Importantly, photoactivated 1 kills not only differentiated RD cells but also even more effectively cancer stem cells (CSCs) of RD. One of the factors responsible for the activity of irradiated 1 in RD CSCs is its ability to produce ROS in these cells more effectively than in differentiated RD cells. Moreover, photoactivated 1 caused in RD differentiated cells and CSCs a significant decrease of mitochondrial membrane potential and promotes opening mitochondrial permeability transition pores in these cells, a mechanism that has never been demonstrated for any other metal-based anticancer complex. The results of this work give evidence that 1 has a potential for further evaluation using in vivo models as a promising chemotherapeutic agent for photodynamic therapy of hardly treatable human Rhabdomyosarcoma, particularly for its activity in both stem and differentiated cancer cells.
- MeSH
- Child MeSH
- Iridium pharmacology MeSH
- Coordination Complexes * pharmacology MeSH
- Humans MeSH
- Mitochondria MeSH
- Cell Line, Tumor MeSH
- Neoplastic Stem Cells MeSH
- Antineoplastic Agents * pharmacology MeSH
- Rhabdomyosarcoma * drug therapy MeSH
- Check Tag
- Child MeSH
- Humans MeSH
- Publication type
- Journal Article MeSH
Four bipyridine-type ligands variably derivatized with two bioactive groups (taken from ethacrynic acid, flurbiprofen, biotin, and benzylpenicillin) were prepared via sequential esterification steps from commercial 2,2'-bipyridine-4,4'-dicarboxylic acid and subsequently coordinated to ruthenium(II) p-cymene and iridium(III) pentamethylcyclopentadienyl scaffolds. The resulting complexes were isolated as nitrate salts in high yields and fully characterized by analytical and spectroscopic methods. NMR and MS studies in aqueous solution and in cell culture medium highlighted a substantial stability of ligand coordination and a slow release of the bioactive fragments in the latter case. The complexes were assessed for their antiproliferative activity on four cancer cell lines, showing cytotoxicity to the low micromolar level (equipotent with cisplatin). Additional biological experiments revealed a multimodal mechanism of action of the investigated compounds, involving DNA metalation and enzyme inhibition. Synergic effects provided by specific combinations of metal and bioactive fragments were identified, pointing toward an optimal ethacrynic acid/flurbiprofen combination for both Ru(II) and Ir(III) complexes.
- MeSH
- Iridium chemistry pharmacology MeSH
- Coordination Complexes chemical synthesis chemistry pharmacology MeSH
- Humans MeSH
- Ligands MeSH
- Molecular Structure MeSH
- Tumor Cells, Cultured MeSH
- DNA Damage MeSH
- Cell Proliferation drug effects MeSH
- Antineoplastic Agents chemical synthesis chemistry pharmacology MeSH
- Pyridines chemistry pharmacology MeSH
- Ruthenium chemistry pharmacology MeSH
- Drug Screening Assays, Antitumor MeSH
- Cell Survival drug effects MeSH
- Dose-Response Relationship, Drug MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
In this overview, a short history and current state of the art regarding selected anticancer effective transition metal complexes are briefly described. In view of the fact that this text represents a part of experimental work for which Assoc. Prof. Pavel Štarha, Ph.D. was awarded the Alfred Bader Prize for Bioinorganic and Bioorganic chemistry by the Czech Chemical Society in 2017, the report is focused on the results realized mostly at the Division of Biologically Active Complexes and Molecular Magnets of the Regional Centre of Advanced Technologies and Materials of Palacký University in Olomouc. Some examples of highly cytotoxic complexes of platinum, gold, ruthenium, iridium and palladium are put into a broader context of their relative activities as compared to the generally accepted standard, i.e. cisplatin. Some of the presented compounds can be considered as pharmacologically prospective ones, which deserve to be further deeply evaluated in direction of future possible preclinical and clinical studies. Novelty and potential applicability of some of the developed complexes have been also supported by granting of several national and European patents.
- MeSH
- Cisplatin pharmacokinetics chemistry adverse effects MeSH
- Cytokinins pharmacology chemistry MeSH
- Iridium MeSH
- Coordination Complexes * pharmacology chemistry MeSH
- Antineoplastic Agents * pharmacology chemistry MeSH
- Platinum Compounds history pharmacology chemistry classification radiation effects MeSH
- Publication type
- Research Support, Non-U.S. Gov't MeSH
3-Hydroxycyclopent-1-ene-1-carboxylic acid (HOCPCA (1)) is a potent ligand for high-affinity γ-hydroxybutyric acid binding sites in the central nervous system. Various approaches to the introduction of a hydrogen label onto the HOCPCA skeleton are reported. The outcomes of the feasible C─H activation of olefin carbon (C-2) by iridium catalyst are compared with the reduction of the carbonyl group (C-3) by freshly prepared borodeuterides. The most efficient iridium catalysts proved to be Kerr bulky phosphine N-heterocyclic species providing outstanding deuterium enrichment (up to 91%) in a short period of time. The highest deuterium enrichment (>99%) was achieved through the reduction of ketone precursor 2 by lithium trimethoxyborodeuteride. Hence, analogical conditions were used for the tritiation experiment. [3 H]-HOCPCA selectively labeled on the position C-3 was synthetized with radiochemical purity >99%, an isolated yield of 637 mCi and specific activity = 28.9 Ci/mmol.
- MeSH
- Alkenes chemistry MeSH
- Boron chemistry MeSH
- Deuterium chemistry MeSH
- Hydroxybutyrates chemistry MeSH
- Iridium chemistry MeSH
- Isotope Labeling MeSH
- Catalysis MeSH
- Ligands MeSH
- Oxidation-Reduction MeSH
- Tritium chemistry MeSH
- Deuterium Exchange Measurement * MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
Couples of N-heterocyclic carbene complexes of ruthenium, iridium, platinum, and gold, each differing only in the carbene ligand being either 1,3-dimethylimidazol-2-ylidene (IM) or 1,3-dimethyl-N-boc-O-methylhistidin-2-ylidene (HIS), were assessed for their antiproliferative effect on seven cancer cell lines, their interaction with DNA, their cell cycle interference, and their vascular disrupting properties. In MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assays only the platinum complexes were cytotoxic at single-digit micromolar IC50 concentrations with the (HIS)Pt complex being on average twice as active as the (IM)Pt complex. The former was highly efficacious against cisplatin-resistant HT-29 colon carcinoma cells where the latter had no effect. Both Pt complexes were accumulated by cancer cells and bound to double-helical DNA equally well. Only the (HIS)Pt complex modified the electrophoretic mobility of circular DNA in vitro due to the HIS ligand causing greater morphological changes to the DNA. Both platinum complexes induced accumulation of 518A2 melanoma cells in G2/M and S phase of the cell cycle. A disruption of blood vessels in the chorioallantoic membrane of fertilized chicken eggs was observed for both platinum complexes and the (IM)gold complex. The (HIS)platinum complex was as active as cisplatin in tumor xenografted mice while being tolerated better. We found that the HIS ligand may augment the cytotoxicity of certain antitumoral metal fragments in two ways: by acting as a transmembrane carrier increasing the cellular accumulation of the complex, and by initiating a pronounced distortion and unwinding of DNA. We identified a new (HIS)platinum complex which was highly cytotoxic against cancer cells including cisplatin-resistant ones.
- MeSH
- Imidazoles * chemical synthesis chemistry pharmacology MeSH
- Iridium * chemistry pharmacology MeSH
- Chick Embryo MeSH
- Humans MeSH
- Melanoma drug therapy metabolism pathology MeSH
- Mice MeSH
- Cell Line, Tumor MeSH
- Neovascularization, Pathologic drug therapy metabolism pathology MeSH
- Platinum * chemistry pharmacology MeSH
- Antineoplastic Agents * chemical synthesis chemistry pharmacology MeSH
- Ruthenium * chemistry pharmacology MeSH
- Xenograft Model Antitumor Assays MeSH
- Gold * chemistry pharmacology MeSH
- Animals MeSH
- Check Tag
- Chick Embryo MeSH
- Humans MeSH
- Mice MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
The cellular mechanism of action of an iridium(III) half-sandwich complex [(η(5)-C5Me4C6H4C6H5)Ir(phen)Cl]PF6 (phen = phenanthroline) (1) is reported. Complex 1 was used to treat several cell lines, including cisplatin-sensitive, cisplatin-resistant (with intrinsic and acquired resistance) carcinoma cells with wild type p53 status as well as the cells with no intact p53 gene, and nontumorigenic cells. Complex 1 preferentially kills cancer cells over nontumorigenic cells and exhibits no cross-resistance with cisplatin. It appears to retain significant activity in human tumor cell lines that are refractory or poorly responsive to cisplatin, and in contrast to cisplatin it displays a high activity in human tumor cell lines that are characterized by both wild type and mutant p53 gene. The mechanism of cell killing was established through detailed cell-based assays. Complex 1 exhibits dual effects in killing cancer cells causing nuclear DNA damage and mitochondrial dysfunction involving ROS production simultaneously. Flow cytometric studies and impedance-based monitoring of cellular responses to 1 demonstrated that 1 acts more quickly than cisplatin to induce cell death and that 1 is a more effective apoptosis inducer than cisplatin in particular in early stages of treatment, when the apoptotic effects predominate over necrosis. Overall, our findings confirm that 1 and its iridium derivatives represent promising candidates for further pre-clinical studies and new additions to the growing family of nonplatinum metal-based anticancer complexes.
- MeSH
- Apoptosis drug effects MeSH
- Cisplatin pharmacology MeSH
- Iridium pharmacology MeSH
- Humans MeSH
- Cell Line, Tumor MeSH
- Antineoplastic Agents pharmacology MeSH
- Flow Cytometry MeSH
- Reactive Oxygen Species metabolism MeSH
- Check Tag
- Humans MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
The effect of replacement of the N,N-chelating ligand 1,10-phenanthroline (phen) in the Ir(III) pentamethylcyclopentadienyl (Cp*) complex [(η(5)-Cp*)(Ir)(phen)Cl](+) (2) with the C,N-chelating ligand 7,8-benzoquinoline (bq) to give [(η(5)-Cp*)(Ir)(bq)Cl] (1) on the cytotoxicity of these Cp*Ir(III) complexes toward cancer cell lines was investigated. Complex 2 is inactive, similar to other Cp*Ir(III) complexes containing the N,N-chelating ligands. In contrast, a single atom change (C(-) for N) in the chelating N,N ligand resulted in potency in human ovarian carcinoma cisplatin-sensitive A2780 cells, and, strikingly, 1 is active in the cisplatin-resistant human breast cancer MCF-7 and A2780/cisR cells. Replacement of the N,N-chelating ligand with the C,N-chelating ligand gives rise to increased hydrophobicity, leading to higher cellular accumulation, higher DNA-bound iridium in cells and higher cytotoxicity. The pathways involved in cellular accumulation of 1 have been further explored and compared with conventional cisplatin. The results show that both energy-independent passive diffusion and energy-dependent transport play a role in accumulation of 1. Further results were consistent with involvement of p-glycoprotein, multidrug resistance-associated protein 1 and glutathione metabolism in the efflux of 1. In contrast, the internalization of 1 mediated by the endocytotic uptake pathway(s) seems less likely. Understanding the factors which contribute to the mechanism of cellular accumulation of this Ir(III) complex can now lead to the design of structurally similar metal complexes for antitumor chemotherapy.
- MeSH
- Chelating Agents chemistry pharmacokinetics pharmacology MeSH
- Drug Resistance, Neoplasm MeSH
- Cisplatin pharmacology MeSH
- Iridium chemistry pharmacokinetics pharmacology MeSH
- Coordination Complexes chemistry pharmacokinetics pharmacology MeSH
- Humans MeSH
- Cell Line, Tumor MeSH
- Breast Neoplasms drug therapy metabolism MeSH
- Multidrug Resistance-Associated Proteins metabolism MeSH
- Antineoplastic Agents chemistry pharmacokinetics pharmacology MeSH
- Check Tag
- Humans MeSH
- Female MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- MeSH
- Pharmacology MeSH
- Drug Therapy MeSH
- Homeopathy MeSH
- Iridium pharmacology therapeutic use MeSH
- Pharmaceutical Preparations MeSH
- Humans MeSH
- Adolescent MeSH
- Attention drug therapy MeSH
- Check Tag
- Humans MeSH
- Adolescent MeSH
- Male MeSH
- Publication type
- Case Reports MeSH
